docs: def cell_hash(self, cell, cell_index):
          """
          Compute cell hash based on cell index and cell content
          :param cell: cell to be hashed
          :param cell_index: cell index
          :return: hash string
          """
          s = '{uid} {cell} {index}'.format(uid=self.uid,
                                            cell=str(cell.source),
                                            index=cell_index).encode('utf-8')
  
          hash = hashlib.sha1(s).hexdigest()[:8]
          return hash